body {
    width: 100%;
    min-width: 320px;
    max-width: 640px;

    margin:0 auto;

    font-size: 14px ;
    /* 优先找苹果字体，苹果字体没有，向后匹配 */
    font-family: -apple-system, Helvetica, sans-serif;
    color: #666;
    /* ? */
    line-height: 1.5 ;

    background-color: #ccc;
}

img {
    /* 在一个大盒子里消除img和div盒子之间空隙 */
    vertical-align: middle;
}

ul {
    margin: 0;
    padding: 0;
    list-style: none;
}

a {
    color: #666 ;
    text-decoration: none ;
}

.clearfix:after {
    visibility: hidden;
    display: block;
    font-size: 0;
    content: " ";
    clear: both;
    height: 0;
  }

.open-app {
    height: 45px;

}

.open-app ul li {
    float: left ;
    height: 45px;
    line-height: 45px;
    text-align: center;
    background-color: #333333;
    color: #fff;
}

.open-app ul li:nth-child(1) {
    width: 8%;
}
.open-app ul li:nth-child(1) img {
    width: 10px;
}
.open-app ul li:nth-child(2) {
    width: 10%;
}
.open-app ul li:nth-child(2) img {
    width: 30px;
    vertical-align: middle;
}
.open-app ul li:nth-child(3) {
    width: 57%;
}
.open-app ul li:nth-child(4) {
    width: 25%;
    background-color: #f63515;
}

/* 搜索 */
.search-wrap {
    /* 知识点：overflow hidden使用场景，回头看笔记 */
    overflow: hidden;

    /* position: relative; 由relative改为fixed。将来内容向上滑动时该UI固定不动 */
    position: fixed;
    width: 100%;
    height: 44px;
    min-width: 320px;
    max-width: 640px;
    /* background-color: #C62722; */
}

.search-category {
    /* display: none; */
    position: absolute;
    top: 0;
    left: 0;
    width: 40px;
    height: 44px;
}

.search-category::before {
    /* 伪元素，content必填 */
    content: '';
    /* 它的作用：转成块元素 因为是在div之前 */
    display: block;
    width: 20px;
    height: 18px;
    background: url(../images/jd-category.png) no-repeat;
    /* css3 背景缩放 */
    background-size: 20px 18px ;
    margin: 14px 0 0 15px;
}

.search-login {
    /* display: none; */
    position: absolute;
    top: 0;
    right: 0;
    width: 40px;
    height: 44px;
    line-height: 44px;
    color: #fff;
    text-align: center;
}

.search {
    position: relative;
    /* 不能浮动，必须作为标准流 。思考为何。再看css经典布局  */
    /* 圣杯布局：左右固定，中间自适应 */
    /* float: left; */
    height: 30px;
    /* width: 100%; */
    margin: 7px 50px;
    background-color: #fff;
    border-radius: 15px;

}

.sbcy-icon {
    position: absolute;
    top: 4px;
    left: 10px;
    width: 22px;
    height: 22px;
    background:url(../images/shibochuye.v1.png) no-repeat ;
    background-size: 22px 22px;
}

.sbcy-icon::after {
    content: '';
    position: absolute;
    top: 0;
    right: -6px ;

    width: 1px;
    height: 20px;
    background-color: #ccc;
}

.query {
    position: absolute;
    top: 4px;
    left: 45px;

    height: 22px;
    width: 22px;
    background:url(../images/query.png) no-repeat;
    background-size: 22px 22px;

}

.main-slider img {
    width: 100%;
}

/* 左中右广告 */
.main-advertise div {
    float: left;
    width: 33.33%;

}

/* 中部3张图样式 */
.main-advertise div img {
    width: 100%;
    height: 100%;
} 
.main-advertise div:nth-child(2) img {
    width: 9.75rem;
    height: 5.75rem; 
} 

/* 中部小图广告 */
.main-small-advertise {
    /* 若图片过大，则溢出隐藏，显示盒子效果 */
    overflow: hidden;
    background-color: #fff;
    border-radius: 15px;
}
/* 
注：在一个大盒子里消除img和div盒子之间空隙，对 img设置vertical-align: middle;
详看最上册 img的标签设置
*/
.main-small-advertise img {
    width: 100%;
}

nav a {
    float: left;
    width: 20%;
    /* 就是这里为什么用它就实现了居中？ */
    text-align: center;
}

nav a img {
    width: 40px;
    /* margin: 10px auto; */
    margin-top: 10px;
}

nav a span {
    display: block;
}

/* 
    css3 的盒子模型：
    box-sizing: border-box;
*/